What did the anti-federalists want added to the constitution before they would agree to ratify it? a. a declaration of human rights b. a system of checks and balances on the federal government c. a bill of rights d. the federalist papers

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.